1,3-Butadiene is not known as a natural product, but it is a ubiquitous environmental pollutant and mainly originates from combustion products (motor vehicle emissions, tobacco smoke). Butadiene is also released into the atmosphere from smoke from fires, burning plastics, and evaporation from petrol. In the United Kingdom in 1996, the estimated emission of butadiene in road vehicle exhaust was 68%, and emissions from machinery were 14%. The remaining emissions came from the chemical industry. Products containing butadiene are incorporated into automotive components, building materials, appliance parts, computers and telecommunications equipment, clothing, protective clothing, packaging, and household items. Butadiene is also used as an intermediate in the production of chloroprene, adiponitrile, and other basic petrochemicals. The strongest evidence exists for an association with non-Hodgkin’s lymphoma (study of workers in the monomer industry). The following urinary metabolites were identified: 1,2-dihydroxybutyl mercapturic acid (DHBMA) and monohydroxy-3-butenyl mercapturic acid (MHBMA).